Search NASA⌕ Search

SEARCH · Search NASA

Results for “BEAUTY BARYONS”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 records

Baryogenesis from oscillations of charmed or beautiful baryons

Here, we propose a model for CP violating oscillations of neutral, heavy-flavored baryons into antibaryons at rates which are within a few orders of magnitude of their lifetimes. The flavor structure of the baryon violation suppresses neutron oscillations and baryon number violating nuclear decays to experimentally allowed rates. We also propose a scenario for producing such baryons in the early Universe via the out-of-equilibrium decays of a neutral particle, after hadronization but before nucleosynthesis. We find parameters where CP violating baryon oscillations at a temperature of a few MeV could result in the observed asymmetry between baryons and antibaryons. Additionally, part of the relevant parameter space for baryogenesis is potentially testable at Belle II via decays of heavy flavor baryons into an exotic neutral fermion. The model introduces four new particles: three light Majorana fermions and a colored scalar. The lightest of these fermions is typically long lived on collider timescales and may be produced in decays of bottom and possibly charmed hadrons.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of matter–antimatter differences in beauty baryon decays

Differences in the behaviour of matter and antimatter have been observed in K and B meson decays, but not yet in any baryon decay. Such differences are associated with the non-invariance of fundamental interactions under the combined charge-conjugation and parity transformations, known as CP violation. Here, using data from the LHCb experiment at the Large Hadron Collider, we search for CP-violating asymmetries in the decay angle distributions of Λ$^0_b$ baryons decaying to pπ - π + π - and pπ - K + K - final states. These four-body hadronic decays are a promising place to search for sources of CP violation both within and beyond the standard model of particle physics. We find evidence for CP violation in Λ$^0_b$ to pπ - π + π - decays with a statistical significance corresponding to 3.3 standard deviations including systematic uncertainties. This represents the first evidence for CP violation in the baryon sector.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurements of Direct CP Violating Asymmetries in Charmless Decays of Strange Bottom Mesons and Bottom Baryons

We report measurements of direct CP--violating asymmetries in charmless decays of neutral bottom hadrons to pairs of charged hadrons with the upgraded Collider Detector at the Fermilab Tevatron. Using a data sample corresponding to 1 fb{sup -1} of integrated luminosity, we obtain the first measurements of direct CP violation in bottom strange mesons, A{sub CP}(B{sub s}{sup 0}{yields}K{sup -}{pi}{sup +})=+0.39{+-}0.15(stat){+-}0.08(syst), and bottom baryons, A{sub CP}({Lambda}{sub b}{sup 0}{yields}p{pi}{sup -})=+0.03{+-}0.17(stat){+-}0.05(syst) and A{sub CP}({Lambda}{sub b}{sup 0}{yields}pK{sup -})=+0.37{+-}0.17(stat){+-}0.03(syst). In addition, we measure CP violation in B{sup 0}{yields}K{sup +}{pi}{sup -} decays with 3.5{sigma} significance, A{sub CP}(B{sup 0}{yields}K{sup +}{pi}{sup -})=-0.086{+-}0.023(stat){+-}0.009(syst), in agreement with the current world average. Measurements of branching fractions of B{sub s}{sup 0}{yields}K{sup +}K{sup -} and B{sup 0}{yields}{pi}{sup +}{pi}{sup -} decays are also updated.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

QCD factorization for {Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -}

We prove that in the limit m{sub b},m{sub c}{yields}{infinity}, with m{sub c}/m{sub b} fixed, factorization holds at order {alpha}{sub s} for the decay {Lambda}{sub b}{sup 0}{yields}{Lambda}{sub c}{sup +}{pi}{sup -}. This proof is done in the infinite-momentum frame in which the momenta of {pi}, {Lambda}{sub c}, and {Lambda}{sub b} go to infinity. Our result is renormalization-scale- and scheme-independent at O({alpha}{sub s}). This is the same as the QCD factorization for B{yields}D{pi}.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

B hadrons spectroscopy at the D0 experiment

The latest results on B hadron spectroscopy from the DOe experiment at the Tevatron are presented. The mass measuremen of the B{sub c}{sup -} meson in the B{sub c}{sup -}{yields}J/{psi}{pi}{sup -} decay channel, the observation of excited B{sub s} mesons, the first direct observation of the {Xi}{sub b}{sup -} baryon, and the first observation of the {Omega}{sub b}{sup -} baryon.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Heavy flavor baryon states at the Tevatron

Precision measurements of the masses and widths of the bottom baryon resonances {Sigma}{sub b} and {Sigma}*{sub b} and charm baryons {Lambda}{sub c}(2595), {Lambda}{sub c}(2625), {Sigma}{sub c}(2455), and {Sigma}{sub c}(2520) are reported. A new measurement of {Lambda}{sub b} production is described. The studies include the first measurement of the widths and isospin mass splittings of the members of the {Sigma}{sub b} family. The charm baryons are examined through their strong decays to the {Lambda}{sub c} ground state, and measurements of their mass differences relative to the ground state, and corresponding decay widths, are reported. The data were collected by the CDF and D0 detectors for 1.96 TeV proton-antiproton collisions during Run II at the Fermilab Tevatron.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Charmed Bottom Baryon Spectroscopy

The arena of doubly and triply heavy baryons remains experimentally unexplored to a large extent. This has led to a great deal of theoretical effort being put forth in the calculation of mass spectra in this sector. Although the detection of such heavy particle states may lie beyond the reach of experiments for some time, it is interesting to compare results between lattice QCD computations and continuum theoretical models. Several recent lattice QCD calculations exist for both doubly and triply charmed as well as doubly and triply bottom baryons. In this work we present preliminary results from the first lattice calculation of the mass spectrum of doubly and triply heavy baryons including both charm and bottom quarks. The wide range of quark masses in these systems require that the various flavors of quarks be treated with different lattice actions. We use domain wall fermions for 2+1 flavors (up down and strange) of sea and valence quarks, a relativistic heavy quark action for the charm quarks, and non-relativistic QCD for the heavier bottom quarks. The calculation of the ground state spectrum is presented and compared to recent models.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Spectrum of baryons with one charm quark

Diquark is employed to study the spectrum of baryons with one charm quark and two light quark within the mass loaded flux tube model. The spin-orbit interaction is taken into account based on the heavy quark symmetry. Some observed {Lambda}{sub c} and {Xi}{sub c} baryons are systematically classified with suggested J{sup P} quantum numbers.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Calculation of the heavy-hadron axial couplings g1, g2, and g3 using lattice QCD

In a recent paper [arXiv:1109.2480] we have reported on a lattice QCD calculation of the heavy-hadron axial couplings g{sub 1}, g{sub 2}, and g{sub 3}. These quantities are low-energy constants of heavy-hadron chiral perturbation theory (HH{chi}PT) and are related to the B*B{pi}, {Sigma}{sub b}*{Sigma}{sub b}{pi}, and {Sigma}{sub b}{sup (*)}{Lambda}{sub b}{pi} couplings. In the following, we discuss important details of the calculation and give further results. To determine the axial couplings, we explicitly match the matrix elements of the axial current in QCD with the corresponding matrix elements in HH{chi}PT. We construct the ratios of correlation functions used to calculate the matrix elements in lattice QCD, and study the contributions from excited states. We present the complete numerical results and discuss the data analysis in depth. In particular, we demonstrate the convergence of SU(4|2) HH{chi}PT for the axial current matrix elements at pion masses up to about 400 MeV and show the impact of the nonanalytic loop contributions. Finally, we present additional predictions for strong and radiative decay widths of charm and bottom baryons.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Heavy quark spin symmetry and heavy hadronic molecules

In the heavy quark limit there is heavy quark spin symmetry. As a consequence, heavy hadrons or heavy quarkonia form spin multiplets. We argue that due to the symmetry, also heavy flavor hadronic molecules form spin multiplets, and the hyperfine splittings are the same as those between the heavy hadrons which are components of the molecules. Hence it provides a method to identify the nature of heavy hadronic molecules. As an example, we give predictions of the properties of an {eta}{sub c}{sup '}f{sub 0}(980) bound state assuming the Y(4660) to be an S-wave {psi}{sup '}f{sub 0}(980) shallow bound state. We also show that the enhancement observed in the {Lambda}{sub c}{sup +}{Lambda}{sub c}{sup -} invariant mass distribution might be the Y(4660).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Possible {Lambda}{sub c}N molecular bound state

{Lambda}{sub c}N bound state problem is investigated in the one-meson-exchange potential model. The potentials are obtained from an effective Lagrangian reflecting the heavy quark symmetry, chiral symmetry, and hidden local symmetry. We also consider the contributions from the coupled channels of {Sigma}{sub c}N and {Sigma}{sub c}*N. It is found that the channel coupling is very important in binding the baryons. We find that the formation of the nearly degenerate J{sup P} = 0{sup +} and J{sup P} = 1{sup +} {Lambda}{sub c}N molecular bound states is plausible, although the results are sensitive to the cutoff parameters.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Heavy Hadron Spectroscopy and Production at Tevatron

Using data from p{bar p} collisions at {radical}s = 1.96 TeV recorded by the CDFII and D0 detectors at the Fermilab Tevatron, we present recent results on charm and bottom hadrons. The most recent CDF results on properties of the four bottom baryon resonant states {Sigma}{sub b}{sup (*)-}, {Sigma}{sub b}{sup (*)+}. New results on exotic {Upsilon}(4140) state observed by CDF are also reported. A precise measurement of production rates of the lowest lying bottom baryon, {Lambda}{sub b}{sup 0}, produced in the D0 detector is presented.

43 PARTICLE ACCELERATORS↗

Heavy hadron spectroscopy at CDF

We present recent CDF results on the properties of hadrons containing heavy quarks. These include measurements of charm and {Sigma}{sub b}{sup -}{Sigma}*{sub b}{sup -} baryon's masses, lifetimes and masses of {Omega}{sub b}{sup -}, {Xi}{sub b}{sup -} and B{sub c}{sup -} and a measurement of exclusive B{sup +}, B{sup 0} and {Lambda}{sub b} lifetimes as well as lifetime ratios (charge conjugate modes are implied throughout the text). We also summarize new measurements of exotic particles X(3872) and Y(4140).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for charmonium and charmoniumlike states in Υ ( 2 S ) radiative decays

Using a sample of 158 x 10⁶ Υ(2S) events collected with the Belle detector, charmonium and charmoniumlike states with even charge parity are searched for in Υ(2S) radiative decays. No significant Xcl or nc signal is observed, and the following upper limits at 90% confidence level (C. L.) are obtained: Β(Υ(2S)→YXco)<1.0×10 - ⁴, Β(Υ(2S)→yxc1)<3.6×10 - ⁶, Β(Υ(2S)→yxc2)<1.5 x 10 - ⁵, and Β(Υ(2S)→ync)<2.7×10 - ⁵. No significant signal of any charmoniumlike state is observed, and we obtain the limits Β(Υ(2S)→yX(3872)) x Β(X(3872)→π⁺π⁻J/ψ)<0.8×10-6, Β(Υ(2S)→γX(3872))× Β(X(3872)→ π⁺π⁻π⁰Jlψ)<2.4 x 10⁻⁶, Β(Υ(2S)→γX(3915))× Β(X(3915)→ωJ/ψ)<2.8×10⁻⁶, Β(Υ(2S)→γY(4140)) x Β(Y(4140)→$\phi$J/ψ))<1.2 x 10 - ⁶, and Β(Υ(2S)→yX(4350))× Β(X(4350)→$\phi$J/ψ))<1.3×10⁻⁶ at 90% C. L.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗